Cored welding electrodes are consumable welding devices with a tubular core surrounded by an outer sheath, where the core may include fluxing elements, deoxidizing and denitriding agents, and alloying materials, as well as elements that increase toughness and strength, improve corrosion resistance, and stabilize a welding arc. Flux-cored electrodes include flux within the electrode core to produce an extensive slag cover during welding, which supports and shapes the resulting weld bead. Flux cored arc welding (FCAW) processes employ flux-cored electrodes to provide higher deposition rates than those of other processes without developing excessive electrical resistance heating, even with relatively small diameter electrodes, wherein FCAW is widely used for welding large sections and with materials of great thicknesses and lengths, especially in the flat position. During FCAW processes, the flux from the electrode core produces a slag which covers the weld pool as it is solidifying to protect the weld pool from impurities. Flux cored arc welding is typically an automatic or semi-automatic process having several advantages. Because the process is machine controlled, the weld quality is consistent with fewer defects than manual welding processes. In addition, FCAW allows the use of higher currents and thus facilitates increased weld rates and improved productivity, wherein distortion can be reduced because of lower heat input and higher lineal welding speeds. FCAW may be performed with no shielding gas, a process sometimes referred to as “Innershield” or “self-shielding” (FCAW-S). In such self-shielded FCAW, the heat of the arc causes decomposition and some vaporization of the electrode's flux core, which partially protects the molten metal. Gas shielded flux-cored arc welding (FCAW-G, also known as “Outershield”) employs an external shielding gas, such as argon, carbon dioxide (CO2), or mixtures thereof in conjunction with a flux cored electrode. The combination of a flux inside the electrode core and the external shielding gas yields a good weld from a stable arc with very little spatter. The most widely used shielding gas is CO2, but mixtures of argon and CO2 are becoming more common because the argon gas improves the properties of the weld and provides rapid deposition of metal and high-quality welds in steel. Relatively long electrode extensions or stick-out distances may be employed to preheat the electrode and decrease the welding current, thereby producing a shallow penetrating welding bead. Various types of flux-cored welding electrodes are designed for specific gas-shielded FCAW applications, such as high-speed, single-pass welding, general purpose welding, structural fabrication, and high-strength pipe welding, wherein the constituent materials used in the core and the electrode diameters may be tailored for a given situation.
One problem encountered in gas-shielded FCAW is variously referred to as “gas tracking”, “gas marking”, or “worm tracking”, in which so-called gas marks or tracks appear as a series of depressions in the shape of a “worm” on the weld surface. Gas tracking is the result of gases being trapped under the slag as the weld solidifies, and is most commonly observed when welding at high welding travel speed using a high argon blend shielding gas, such as 75 percent Argon and 25 percent CO2, and/or where small stickout distances are used, wherein the slag cools and solidifies before the gas can escape. One factor that may influence gas tracking is moisture in the flux core, which may be caused by a poor joint seal in the electrode manufacturing process, by storage of the electrode in a damp environment, or by the wire being unprotected when loaded on the wire feeder spool of the welding machine. Efforts to reduce gas marking may include using a higher mixture of CO2 content in the shielding gas (e.g., lowering the argon content), cleaning the weld joint of paint, rust, and moisture, minimizing wind disturbance of the gas shielded FCAW process, removing spatter from inside the shielding gas nozzle, and/or increasing the flow rate of the shielding gas. In addition, preheating the flux cored electrode prior to use may help avoid gas tracking, along with using a slightly longer wire stick out to preheat the electrode and to reduce the potential for hydrogen contamination and gas tracking. Also, increased weld current, lowering the lineal welding travel speed, and/or increasing the weld size all may be used to combat gas tracking. In addition to these process modifications, the selection of flux-cored welding electrodes may affect the likelihood of gas-tracking for a given gas-shielded FCAW application. Accordingly, there is a need for methodologies by which flux-cored welding electrodes can be characterized or rated according to the propensity for gas tracking, by which the informed selection of welding electrodes can be facilitated for specific gas-shielded FCAW processes.